47-59 1957 pickup rear axle?

[MikeB]

A guy on another forum is asking about going to a taller rear axle ratio on a 57 pickup. What type rear end did these trucks use, and are ring & pinion sets available for them?

Or, is there a later model axle, such as 12-bolt truck, that will drop in easily?

Thanks.

[Hcb3200]

I found that a certain Colorado rear end year models are the same track width. (this is the biggest headache). Want to say ours is 2005. I got a 3.73 geared ratio with a locker. (posi) RPO code
G80. We put it in behind the TH350 that was in the truck at the time. We now run a L6.0/6L90 and it hooks at the traffic light starts. and runs really good at hwy speeds and the locker works well in the mud. Suspension is stock all around otherwise on the rear.

if the sticker from salvage yard is correct.
its a 4x2 off road suspension opt z71, 3.73
6.04, 3.4, AOD, G80 RPO codes AOD, G80
2215 B Rear Axle Assembly
year model 2005
Drum brakes were on this one.

it think they have a 3.42 axle ration one as well.

[MJN]

Assuming it is a 1/2ton they originally they came with a GM Eaton-type HO33 axle with either 3.90 or 4.11 gears in them. I don't believe there are aftermarket gears available for them any more.
The options for different ratios are sort of limited to a different rear axle such as a 12 bolt and relocating the spring perches or adding an OD transmission or auxiliary OD unit.

The 3/4 and 1 tons came with GM Eaton-type HO52 and 72 axles with 4.56 or 5.14 gears. 4.56's were not available in the 1 tons. There are no aftermarket gears for these axles and would again require replacing with a GM 14 bolt (or similar) and relocating the spring perches and shock mounts. You could replace the third member with one with 4.11's but that is the best you'll find for the Eaton-type axle.

[MikeB]

Thanks, guys.

Also, a guy on the other forum said a square body 8.5" 10-bolt is a near bolt-in conversion.

[1project2many]

Toyota truck axles from the '90s fit right in. Toyota axles have many more gear ratios available. And the six lug pattern from a 4X4 truck fits original wheels.

[paulspickupparts]

I have a 3.08 rear from a 64 . You would have to put spring perches but is a 6 bolt and would give you great cruising speeds . I might have a 62 Auto rear end but will have to be warmer weather to pull out. Thanks

[mr48chev]

I think little snooping on the Colorado forums will give you rear axle wms to wms (3 different widths, I think). it will also get you the rear axle gear ratio codes. 6 lug Chevy stayed the same wms to wms up through 68, but same year GMC have leaf springs. They
got wider in 69 and wider yet in 73.

I'm not up on the Toyota axles.

I'm still not at my computer much, so research isn't going to be easy for me right now .

[Divine 59]

Yukon gear offers a 3.38 R&P but it is listed as out of stock currently.

https://www.yukongear.com/shop/yg-gm55t-338

[G&R's57GMC]

To the original poster , what tire diameter are you planning to run ?

My ‘57 had 7.00 x 14 with 3.90 gears it was a bit much until I put tires from my Avalanche that are 32” diameter they really calmed things down like changing gears . But if you’re stock or lower they may rub .
I put 30” diameter tires on my ‘56 stock height with 3.90 gears and made ok on the freeway.

[dsraven]

are you looking for a gear set or a whole different axle?
if looking for a whole different axle assembly you can just google track width for donor axles and pick from a list. bear in mind that some of these are goint to include the brake drums or rotors and some will be dimensions from the actual axle flanges. if a little work is ok with you then the ford 8.8 axle is a oretty tough alternative, info on those can be found at the ranger statin. ford explorer is a common donor, they can be had with large axles, 3.73 gears, disc brakes with internal park brake and posi. the explorer has an offset center section but what a lot of guys do is shorten the long side to be the same as the short side and then simply use a short side axle on both sides. they have a 5 stud wheel boly pattern which can be a little tricky to drill to a 6 bolt pattern if thats what you want. not impossible though. easier if you are ok with a 5 stud wheel or are changing the front to a 5 bolt anyway. googleshortening an 8.8 axle if that interests you, or check for an axle from a mustang which would have a centered middle section.
personally I would use the newest axle I could get my hands on because of parts availability and also because of the wear factor on older parts and replacement parts prices. if you are looking for a different axle and plan to replace everything inside and build a narrowed unit capable of high horespower etc etc that is a whole different ball game. if looking for something to install simply for updating the gears so the engine can handle higher road speeds and you are ok with drum brakes etc then it may be worth a trip to the local pick n pull with a tape measure and a helper or at least something you can use to bolt on or magnet onto the axle flanges for a more acurate dimension check. a plumb bob would also work if you drop the plumb bob from each axle and mark the ground then take dimensions from those points. that would likely require some cutting off of old mounts and welding in some new spring perches on the new axle. spring perches can be bought from a local trailer axle supply distributor. be careful when cutting or welding so as not to get too much heat on the axle tubes or they may warp or bend as they cool
you could also install an overdrive trans which would give you less engine rpm at highway speeds. there are rpm calculators online that can figure that out for you if you know your tire height, trans final gear ratio and a speed to work with.

[mr48chev]

As far as choosing a gear ratio this calculator is real easy to use http://advanced-ev.com/Calculators/TireSize/
Don't laugh because it is for electric rigs, you can plug in any three factors and get the fourth. You do have to factor the overdrive ratio of an overdrive transmission in the rear end gear ratio of the rig has OD.

I snooped on the Colorado forums today but couldn't come up with the info I was looking for. On one of them someone had posted rear axle widths for various models and had posted the codes for gear ratios.

Three ratios is what I find
GT4 Rear axle, 3.73 ratio
GT5 Rear axle, 4.10 ratio
GU6 Rear axle, 3.42 ratio

[TonyMann]

I had a 55.5 GMC once, and I used a Rear end from a 1968 Impala with a t h 350 trans, and 372 ratio and because I used 53 car hubs on my straight axle the bolt pattern matched. You will however need to clean off the coil spring hangers and put your spring perches on.

[JDarby]

I have a 3.08 I believe in my 55.1 at the moment that I will give to you if you want to come a get it.
I'm in Texas
It has the spring perch's on it!